Sophie Hartley, age ten, does not want to be a teenager. She vows she'll never be like her older sister, Nora, who has tantrums about her hair and almost everything else. Her older brother Thad is preoccupied with his girlfriend of the moment and doesn't seem to like the family anymore. No, Sophie likes being who she is right now, helping out at home, doing art projects, and hanging out with her two best friends. And another thing. Next year Sophie's class will see the movie about body changes, and her classmates are already buzzing about it. Sophie doesn't want to know about that embarrassing stuff yet. Does that mean she's immature? How can she prove otherwise?